CHROMOSOME NUMBERS IN THE GENUS ONCIDIUM AND ALLIED GENERA A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAII IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN HORTICULTURE SEPTEMBER 1971 By Uthal Charanasri Thesis Committee: Haruyuki Kamemoto, Chairman Richard Hartmann Yoneo Sagawa We certify that we have read this thesis and that in our opinion it is satisfactory in scope and quality as a thesis for the degree of Master of Science in Horticulture. THESIS COMMITTEE Chairman il TABLE OF CONTENTS Page LIST OF TABLES .................................................. iii LIST OF ILLUSTRATIONS........................................ iv INTRODUCTION .................................................. 1 REVIEW OF LITERATURE .......................................... 2 MATERIALS AND METHODS ........................................ 5 Plant M a t e r i a l .......................................... 5 Methods .................................................. 5 RESULTS AND DISCUSSION ........................................ 25 SUMMARY ...................................................... 42 LITERATURE CITED .............................................. 43 iii LIST OF TABLES Table Page I LIST OF SPECIES INVESTIGATED ........................... 6 II CHROMOSOME NUMBERS OF ONCIDIUM SPECIES INVESTIGATED . 26 III CHROMOSOME NUMBERS OF SPECIES IN SOME GENERA RELATED TO ONCIDIUM INVESTIGATED... ..................... 28 iv LIST OF ILLUSTRATIONS Page PLATE I. VEGETATIVE AND FLORAL CHARACTERISTICS OF ONCIDIUM SPECIES .................................... 11 Figure 1 0. lanceanum (O.IX). 2 0. bicallosum (0.25X). 3 0. bicallosum (l.OX). 4 0. luridum (O.IX). 5 0. stramineum (0.12X). 6 0. stramineum (1.8X). 7 0. luridum (1.6X). 8 0. carthagenense (1.8X). 9 0. carthagenense (0.1). PLATE II. VEGETATIVE AND FLORAL CHARACTERISTICS OF ONCIDIUM SPECIES ................................... 13 Figure 10 0. microchilum (O.IX). 11 0. mlcrochilum (1.7X). 12 0. splendldum (O.IX). 13 0. splendidum (1.2X). 14 0. cebolleta (0.2X). 15 0. cebolleta (1.7X). 16 0. nudum (2.OX). 17 0. stipitatum (0.12X). 18 0. stipitatum (1.7X). 19 0. nudum (0.12X). Page PLATE III. VEGETATIVE AND FLORAL CHARACTERISTICS OF ONCIDIUM SPECIES................................... 15 Figure 20 0. desertorum (l.OX). 21 0. desertorum (0.3X). 22 0. lucayanum (1.5X). 23 0. lucayanum (0.3X). 24 0. bahamense (0.8X). 25 0. bahamense (0.25X). 26 0. pulchellum (0.IX). 27 0. haitiense (0.2X). 28 0. haitiense (1.7X). 29 0. pulchellum (l.OX). 30 0. variegatum (1.2X). 31 0. variegatum (0.15X). PLATE IV. VEGETATIVE AND FLORAL CHARACTERISTICS OF ONCIDIUM SPECIES ................................... 17 Figure 32 0. triquetrum (0.3X). 33 0. triquetrum (2.OX). 34 0. henekenii (2.OX). 35 0. pulvinaturn (0.2X). 36 0. pulvinatum (l.OX). 37 0. papilio (0.6X). 38 0. papilio (O.IX). 39 0. ampliatum (0.2X). 40 0. ampliatum (1.5X). VI Page PLATE V. VEGETATIVE AND FLORAL CHARACTERISTICS OF ONCIDIUM SPECIES .................................... 19 Figure 41 0. maculatum (l.OX). 42 0. maculatum (0.15X). 43 0. tigrinum (0.2X). 44 0. tigrinum (l.OX). 45 0. onusturn (0.2X). 46 0. onustum (2.OX). PLATE VI. VEGETATIVE AND FLORAL CHARACTERISTICS OF ONCIDIUM SPECIES ................................... 21 Figure 47 0. 48 0. 49 0. 50 0. 51 0. 52 0. 53 0. 54 0. 55 0. 56 0. vii Page PLATE VII. VEGETATIVE AND FLORAL CHARACTERISTICS OF SPECIES IN GENERA RELATED TO ONCIDIUM . 23 Figure 57 Odontoglossum cariniferxim (1.5X). 58 Odontoglossum cariniferum (0.2X). 59 Odontoglossum grande (0.6X). 60 Odontoglossum grande (O.IX). 61 Miltonia flavescens (0.25X). 62 Brassia maculata (0.25X). PLATE VIII. SOMATIC CHROMOSOMES OF ONCIDIUM SPECIES (1650X). WITH SEPARATED SATELLITES INDICATED BY ARROWS . 30 Figure 63 0. lanceanum (2n = 26). 64 0. haematochilum (2n = 28). 65 0. bicallosum (2n = 28). 66 0. carthagenense (2n = 30). 67 0. luridum (2n = 30). 68 0. stramineum (2n = 30). viii Page PLATE IX. SOMATIC CHROMOSOMES OF ONCIDIUM SPECIES (1650X)..................................... 32 Figure 69 0. stipitatum (2n = 36). 70 0. nudum (2n = 36). 71 0. cebolleta (tetraploid form 2n = 72). 72 0. microchilum (2n = 36). 73 0. splendidum (2n = 36). 74 0. papilio (2n = 38). 75 0. papilio 'Latour's' selfed (2n = 38). PLATE X. SOMATIC CHROMOSOMES OF ONCIDIUM SPECIES (I650X)...................................... 34 Figure 76 0. desertorum (2n = 40). 77 0. henekenii (2n = 40). 78 0. haitiense (2n = 40). 79 0. pulchellum (2n = 42). 80 0. triquetrum (2n = 42). 81 0. variegatum (2n = 42) . 82 0. bahamense (2n = 84). ix Page PLATE XI. SOMATIC CHROMOSOMES OF ONCIDIUM SPECIES (1650X).............. 36 Figure 83 0. pulvinatum (2n = 42). 84 0. ampliatum (2n = 44). 85 0. baueri (2n = 56). 86 0. onustum (2n = 56). 87 0. maculatum (2n = 56). 88 0. ansiferum (2n = 56). 89 0. sarcodes (2n = 56). 90 0. floridanum (2n = 56). 91 0. stenotis (2n = 56). 92 0. ensatum (2n = 56). PLATE XII. SOMATIC CHROMOSOMES OF SPECIES i RELATED TO ONCIDIUM (1650X). 38 Figure 93 Rodriguezla venusta (2n = 42). 94 Odontoglossum grande (2n = 44) 95 Odontoglossum cariniferum (2n 96 Brassia allenii (2n = 50). 97 Brassia gireoudiana (2n = 60). 98 Gomesa crispa (2n = 56). 99 Miltonia flavescens (2n = 60). INTRODUCTION The Oncldium genus comprises 450 to 750 valid species (Schultes, 1960; Hawkes, 1965). It is large and polymorphic. All of the species in this genus are native of tropical and subtropical America being widely distributed from Florida and Mexico through West Indies and Central America to Argentina. The species exhibit diverse vegetative and floral structures. They inhabit hot sea-level to cool mountainous areas. Some of the genera allied to Oncldium have common habitats and may produce Intergeneric hybrids when crossed with Oncldium. Chromosome numbers of seventy-six Oncldium species and forty-two species in related genera have been recorded to date. The somatic chromosome numbers show a wide range from 10 to 168. The production of successful interspecific and intergeneric Oncldium hybrids appears to be possible among species with different chromosome numbers. The present study involved chromosome counts of available species in Oncldium and allied genera Including Odontoglossum, Gomesa, Miltonia, Rodriguezia, Brassia and Comparettia. The objective of this Investigation was to determine the chromosome numbers of species in Oncldium and allied genera and to correlate variations in number with species relationships. REVIEW OF LITERATURE The genus Oncidlum Sw, is one of the largest and most complex genera in the Orchidaceae (Correll, 1950; Hawkes, 1965; Schultes, 1960). It comprises members that are epiphytic, terrestrial, or lithophytic. The pseudobulbs are variously shaped and generally conspicuous. The pseudobulb is one, two, or many-leaved, subtended by foliaceous or papery bracts. Some species are pseudobulbless. The leaf is subcoriaceous to fleshy-coriaceous, and equitant, flat, or terete. The inflorescence is simple or branched, and one- or more-flowered. One or several inflorescences are produced laterally from the base of the pseudobulb, or in the nonpseudobulbous species from the leaf axil. The flowers are variable in size from extremely small to large and showy and are usually yellow or brownish but occasionally white, red, or magenta. The floral bract is small. The sepals are subequal, spreading or reflexed, and free. The petals are subequal to or larger than the dorsal sepal. The lip is adnate to the base of the column and usually forms a right angle with the column. The lip is entire or three or more-lobed with the apical lobe usually much larger than the other lobes. The disk of the lip is usually tuberculate or cristate. The column is short, stout, usually with lateral petaloid auricles at the apex, footless or occasionally with an incipient foot. The clinandrium is truncate, entire or apically two-dentate. The capsule is usually beaked, and is ovoid to ellipsoid fusiform. The anther consists of two pollinia. Dodson (1958) noted that the species were botanically difficult to separate and that a precise generic description was difficult to compile. The placement of the Oncidium alliance was changed several times by different taxonomists. Bentham and Hooker (1883) placed it in the 3 the subtribe Oncidieae, tribe Vandeae. Schlechter (1926) divided the Oncidium alliance into many subtribes based on floral and vegetative characteristics of the plants. Dressier and Dodson (1960) proposed a new classification, placing all genera of the alliance in the subtribe Oncidiinae. The sectional classification of Oncidium attracted the attention of several orchid taxonomists. Lindley (1855) described 209 species of Oncidium and classified the genus into fourteen sections. Pfitzer (1889) arranged Oncidium into seventeen sections and listed seven other related genera. Kranzlln (1922) published a monograph of the genus and classified these species into eighteen sections. Garay (1970), within the framework established by Kranzlin, proposed a reappraisal of the genus Oncidium Sw., incorporating the genus Cyrtochllum and some species of Odontoglossum into the twenty-five sections including all existing type specimens and species described since 1922. Although the first chromosome count of Oncidium was made by Afzelius in 1916, most of the chromosome counts have been accumulated within the last fourteen years. Afzelius recorded the gametic number of Oncidium praetextum as n = 28. Hoffmann (1929, 1930) published the chromosome numbers of four Oncidium